Breather filters enable the ingression and egression of gas into reservoirs of oils, hydraulic fluids, and fuels when the fluid level of the reservoir changes. It is desirable to remove moisture from the air that is being drawn into the reservoir, such that the oil or hydraulic fluid is protected from moisture. During egression of the gas from the reservoir, it is desirable to filter that air from contaminants so that the ambient air surrounding the reservoir is not polluted.
Prior systems have used breather filters having a single adsorbent bed, which become quickly saturated with water when exposed to humid environments, even with no flow. Improvements are desirable.